The financing was a major source of money for building single-family homes and apartments in 1985. The House has passed a tax reform bill with extensive constraints on housing bonds. The bill has gone to the Senate.

In the meantime, bond activity is at a standstill, said Judd Levy, managing director of Merrill Lynch Capital Markets in New York.

Appearing Sunday at a finance session of the National Association of Home Builders, Levy said bond buyers are waiting for ''absolute clarity'' on the law.

Noting there was a rush by both bond buyers and sellers in December to beat potential tax law changes, Levy said that ''as far as I know, not a single housing deal has been done this year.''

Carl Riedy, executive vice president of the Council of State Housing Agencies in Washington, said that last year, state and local housing finance authorities issued about $30 billion in federal income tax-exempt bonds. That money provided mortgages at below-market interest rates to about 300,000 first-time home buyers, he said.

In metropolitan Orlando last year, most new apartment construction was financed through tax-exempt bonds. Developers qualify for the financing by agreeing to set aside a percentage of the apartments for low- and moderate- income tenants.

The House-approved tax reform bill toughens requirements to report on meeting the law's provisions and tilts the program more toward low- and moderate-income renters and buyers.

Bonds sold under the program provide financing at below-market rates because investors, exempted from paying federal income tax on the interest earned, are willing to accept lower yields.

Changes already approved by the House will greatly dampen the bond programs, said Thomas Buckmeyer, second vice president of Smith Barney, Harris Upham and Co. in New York.